As we handed our cameras into the Zodiac and hauled
ourselves inboard my thoughts went over the excellent dive we had
just made. Depth 12m, no current, viz 10m+, temp. 15°C and shoals of
pollock, bib and pouting.

My younger companion as usual started the
questioning. What was a Mulberry Harbour, how large is it, how did it
come to be there off Pagham, Sussex?

For the answers you must look back to World War II
when the invasion of Europe was being planned. The idea was to build
large floating caissons in England at various suitable sites around
the coast and then tow them across to the coast of Normandy and use
them to make a large artificial harbour and so allow the allied
forces to bring men and stores ashore. One has to remember the area
of the invasion had no natural harbour, only miles of sandy beaches,
which were useless to land this vast amount of men and materials
upon. So a prefabricated harbour was designed and built to overcome
the problem.

The 'Far Mulberry' as we know it, was classified as
an 'A1 Caisson', eighty were manufactured, they were 60 ft high, 204
ft in length, 50 ft 3 in wide and had a displacement of 6044 tons.
Draft 20 ft 3 in. The internal walls were 9 in thick with an external
wall size of 15 in.

The A1 units also had Bofars anti-aircraft guns
mounted on steel towers located almost mid-ships and carried a gun
crew and 12 tons of ammunition from the time they were towed away
from the construction berth. When in position the harbours were at
all stages protected by a formidable array of guns at approximately
200 ft spacing all around the outer perimeter, barrage balloons were
also flown from the caissons for added protection.

The caissons when fabricated and completed were
then towed by tugs to special 'waiting parks'. Each unit was designed
to enable it to be gently sunk in shallow water and then when ready
for the tow across the Channel, to be re-floated by simply blowing
the internal tanks by means of valves.

Our one, the 'Far Mulberry' had been in rather
deeper water than originally intended, so It was decided to re-float
it and move it into a shallower position ready for a quick salvage
for D-Day, but owing to a misunderstanding, the necessary tugs were
not on hand to take charge when it came afloat and the flooding
valves were re-opened to allow it to settle on the sea bed again.
Unfortunately the caisson had swung round whilst afloat and it was
forced to settle down again diagonally over a deep depression it had
made on the sea bed. It immediately twisted and cracked beyond
repair.

The unit remained here until early 1945 when it was
finished off by the Royal Air Force in practise bombing runs and that
is the position it now lies in some two nautical miles off Pagham
Beach in 12m of water.

When you next dive the 'Far Mulberry' you will know
a little more of this fascinating wreck and how it came to be there
and when those inevitable questions start from the new divers who
explore these old remains, at least you can give them a brief history
of Caisson Type A1.

If anyone has any photographs or other facts on
this Mulberry section, I would be pleased to hear from them.